March 2022
Intermediate to advanced
682 pages
22h 58m
English
In a DDBS, if the database is either centralized or partitioned so that there is only one copy of each item, and all requests are either local (can be filled at the local site) or remote (can be filled completely at one other site), then the usual locking and timestamping mechanisms are sufficient. More difficult concurrency problems arise when there are multiple copies of data items spread across the system. To solve this multiple-copy consistency problem, we must be sure that each location receives and performs the updates to the common data items. We must also manage compound transactions that require updates to different data items located at different sites. These issues are dealt with ...